Systems and methods for trending patterns within time-series data

ABSTRACT

Systems and methods for trending patterns within a set of time-series data are described. In one or more embodiments, a set of one or more groups of data points that are associated with a particular seasonal pattern are generated within volatile and/or non-volatile storage. A set of pairwise slopes is determined for data point pairs within the set of one or more groups of data points. Based, at least in part on the plurality of pairwise slopes, a representative trend rate for the particular seasonal pattern is determined. A set of forecasted values is then generated within volatile or non-volatile storage based, at least in part, on the representative trend rate for the particular seasonal pattern.

BENEFIT CLAIM; RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Patent Appl. No.62/301,590, entitled “SEASONAL AWARE METHOD FOR FORECASTING AND CAPACITYPLANNING”, filed Feb. 29, 2016, and U.S. Provisional Patent Appln. No.62/301,585, entitled “METHOD FOR CREATING PERIOD PROFILE FOR TIME-SERIESDATA WITH RECURRENT PATTERNS”, filed Feb. 29, 2016, the entire contentsfor each of which are incorporated by reference herein as if set forthin their entirety.

This application is related to U.S. application Ser. No. 15/140,358,entitled “SCALABLE TRI-POINT ARBITRATION AND CLUSTERING”; U.S.application Ser. No. 15/057,065, entitled “SYSTEM FOR DETECTING ANDCHARACTERIZING SEASONS”; U.S. application Ser. No. 15/057,060, entitled“SUPERVISED METHOD FOR CLASSIFYING SEASONAL PATTERNS”; U.S. applicationSer. No. 15/057,062, entitled “UNSUPERVISED METHOD FOR CLASSIFYINGSEASONAL PATTERNS”, and U.S. application Ser. No. 15/266,979, entitled“SYSTEMS AND METHODS FOR DETECTING AND ACCOMMODATING STATE CHANGES INMODELLING”, the entire contents for each of which are incorporated byreference herein as if set forth in their entirety.

TECHNICAL FIELD

The present disclosure relates to computer-implemented techniques forgenerating forecasts. In particular, the present disclosure relates totrending different patterns within a time-series to project futurevalues.

BACKGROUND

Organizations, data analysts, and other entities are often interested inforecasting future values for a time-series signal. In the context ofcapacity planning, for example, a forecast may be used to determine howmany hardware and/or software resources to deploy to keep up withdemand. An inaccurate forecast may result in poor capacity planningdecisions, leading to an inefficient allocation of resources. Forinstance, a forecast that underestimates future demand may lead toinsufficient hardware and/or software resources being deployed to handleincoming requests. As a result, the deployed resources may beover-utilized, increasing the time spent on processing each request andcausing performance degradation. On the other hand, a forecast thatoverestimates future demand may result in too many resources beingdeployed. In this case, the deployed resources may be underutilized,which increases costs and inefficiencies associated with maintaining adatacenter environment.

The approaches described in this section are approaches that could bepursued, but not necessarily approaches that have been previouslyconceived or pursued. Therefore, unless otherwise indicated, it shouldnot be assumed that any of the approaches described in this sectionqualify as prior art merely by virtue of their inclusion in thissection.

BRIEF DESCRIPTION OF THE DRAWINGS

The embodiments are illustrated by way of example and not by way oflimitation in the figures of the accompanying drawings. It should benoted that references to “an” or “one” embodiment in this disclosure arenot necessarily to the same embodiment, and they mean at least one. Inthe drawings:

FIG. 1 illustrates a system in accordance with one or more embodiments;

FIG. 2 illustrates an analytic for generating forecasts based onseasonal pattern trending in accordance with one or more embodiments;

FIG. 3 illustrates an example set of operations for generating aforecast based on seasonal pattern trending in accordance with one ormore embodiments;

FIG. 4A illustrates an example set of operations for classifyingseasonal patterns in accordance with one or more embodiments;

FIG. 4B illustrates an example set of classification results for aseasonal pattern classification in accordance with one or moreembodiments;

FIG. 5A illustrates an example set of operations for grouping datapoints by seasonal pattern and component in accordance with one or moreembodiments;

FIG. 5B illustrates an example set of grouping results in accordancewith one or more embodiments;

FIG. 6A illustrates an example set of operations for determining arepresentative trend rate and intercepts for a set of seasonal patternsin accordance with one or more embodiments;

FIG. 6B illustrate an example set of results for selecting arepresentative trend rate and intercept for different seasonal patternsin accordance with one or more embodiments;

FIG. 7A illustrates an example set of operations for trending patternsusing temporal weighting in accordance with one or more embodiments;

FIG. 7B illustrates an example set of temporally weighted data pointsand pattern trends in accordance with one or more embodiments;

FIG. 8A illustrates an example set of operations for generating aforecast using different trends rates and intercepts for differentseasonal patterns in accordance with one or more embodiments;

FIG. 8B illustrates a difference in forecasts that result fromregression-based trending of a sample and pattern-based trending inaccordance with one or more embodiments;

FIG. 9 illustrates an example computer system on which one or moreembodiments may be implemented.

DETAILED DESCRIPTION

In the following description, for the purposes of explanation, numerousspecific details are set forth in order to provide a thoroughunderstanding. One or more embodiments may be practiced without thesespecific details. Features described in one embodiment may be combinedwith features described in a different embodiment. In some examples,well-known structures and devices are described with reference to ablock diagram form in order to avoid unnecessarily obscuring the presentinvention.

-   -   1. GENERAL OVERVIEW    -   2. ARCHITECTURAL OVERVIEW    -   3. FORECAST ANALYTIC OVERVIEW    -   4. SEASONAL PATTERN DETECTION AND CLASSIFICATION    -   5. DATA POINT GROUPING BY SEASONAL PATTERN AND COMPONENT    -   6. PATTERN TRENDING    -   7. TEMPORALLY WEIGHTED PATTERN TRENDING    -   8. FORECAST GENERATION    -   9. FORECAST UNCERTAINTY BASED ON SEASONAL PATTERN CLASSIFICATION    -   10. SEASONALLY-AWARE CAPACITY PLANNING    -   11. HARDWARE OVERVIEW    -   12. MISCELLANEOUS; EXTENSIONS

1. General Overview

A time-series signal may exhibit various behaviors such as seasonalvariations in peaks and lows, trends, and/or states. A failure toaccount for such characteristics may result in unreliable forecasts and,as previously indicated, poor planning decisions. For instance, amiddleware administrator in charge of a web-service based applicationmay be responsible for ensuring that there are enough hardware and/orsoftware resources during peak times to satisfy demand. Theadministrator may plot a trend line using a linear regression model topredict whether current hardware is sufficient for peak months. However,linear regression does not account for seasonal fluctuations in thetime-series. In the event that online traffic is greatly reduced in thelate evening hours, the linear regression model may underestimate futurepeak values or overestimate future trough values, both of which lead toa wasteful use of computational resources (including computer hardware,software, storage, and processor resources, and any services or otherresources built on top of those resources). Other seasonal factors, suchas increased volume around holidays or sales event, as well asnon-seasonal factors, such as changes in the state of a signal due toexternal factors, may also cause the linear regression model to generateinaccurate forecasts.

Rather than relying on linear regression, an administrator may insteaduse a Holt-Winters forecasting model to account for seasonality in thetime-series. The Holt-Winters forecasting model relies on a tripleexponential smoothing function to model levels, trends, and seasonalitywithin the time-series. A “season” in this context refers to a period oftime before an exhibited behavior begins to repeat itself. The additiveseasonal model is given by the following formulas:

L _(t)=α(X _(t) −S _(t−p))+(1−α)(L _(t−1) +T _(t−1))  (1)

T _(t)=γ(L _(t) −L _(t−1))+(1−γ)T _(t−1)  (2)

S _(t)=δ(X _(t) −L _(t))+(1−δ)S _(t−p)  (3)

where X_(t), L_(t), T_(t), and S_(t) denote the observed level, localmean level, trend, and seasonal index at time t, respectively.Parameters α, γ, δ denote smoothing parameters for updating the meanlevel, trend, and seasonal index, respectively, and p denotes theduration of the seasonal pattern. The forecast is given as follows:

F _(t+k) =L _(t) +kT _(t) +S _(t+k−p)  (4)

where F_(t+k) denotes the forecast at future time t+k.

The additive seasonal model is typically applied when seasonalfluctuations are independent of the overall level of the time-seriesdata. An alternative, referred to as the multiplicative model, is oftenapplied if the size of seasonal fluctuations vary based on the overalllevel of the time series data. The multiplicative model is given by thefollowing formulas:

L _(t)=α(X _(t) /S _(t−p))+(1−α)(L _(t−1) +T _(t−1))  (5)

T _(t)=γ(L _(t) −L _(t−1))+(1−γ)T _(t−1)  (6)

S _(t)=δ(X _(t) /L _(t))+(1−δ)S _(t−p)  (7)

where, as before, X_(t), L_(t), T_(t), and S_(t) denote the observedlevel, local mean level, trend, and seasonal index at time t,respectively. The forecast is then given by the following formula:

F _(t+k)=(L _(t) +kT _(t))S _(t+k−p)  (8)

Predictive models such as triple exponential smoothing are primarilyfocused on generating forecasts about future events. While theHolt-Winter additive and multiplicative models take into accountseasonal indices to generate the forecast, these models provide limitedinformation on any seasonal patterns that may exist in the time-seriesdata. For instance, the seasonal indices represented by equations (3)and (7) operate within the bounds of the forecasting models to whichthey are tied. As a result, the seasonal data output by these formulasdoes not lend itself to meaningful interpretation in contexts outside ofthe specific forecasting models for which the seasonal data wasgenerated. Further, these seasonal indices are typically implemented asinternal structures that are not exposed to the end user. Therefore, theend user may have little or no underlying notion of any of the seasonalpatterns that were used to generate a forecast.

Another deficiency with the Holt-Winters models is that they aredesigned to model time-series with a single seasonal cycle. Manytime-series may be more efficiently and accurately represented asmultiple seasonal patterns mixed together. For example, a given set oftime-series data may have a sparse high signal that trends differentlythan a dense high signal. By merging both patterns, the forecastingmodel may project inaccurate values when there are different types ofseasonal patterns.

Systems and methods for trending patterns within a set of time-seriesdata are described. In one or more embodiments, a set of one or moregroups of data points that are associated with a particular seasonalpattern are generated within volatile and/or non-volatile storage. A setof pairwise slopes is determined for data point pairs within the set ofone or more groups of data points. Based, at least in part on theplurality of pairwise slopes, a representative trend rate for theparticular seasonal pattern is determined. A set of forecasted values isthen generated within volatile or non-volatile storage based, at leastin part, on the representative trend rate for the particular seasonalpattern.

The techniques described herein allow different patterns to be trendedindependently, improving the accuracy of forecasts when patterns trendat different rates. In addition, the use of pairwise slopes to computethe trend rate allows for a robust model in which trends may be moreaccurately modelled for each individual seasonal pattern. Improvedforecasting my lead to enhanced capacity planning, anomaly detection,and other operations within a managed computing system.

2. Architectural Overview

A time series signal comprises a sequence of values that are capturedover time. The source of the time series data and the type ofinformation that is captured may vary from implementation toimplementation. For example, a time series may be collected from one ormore software and/or hardware resources and capture various performanceattributes of the resources from which the data was collected. Asanother example, a time series may be collected using one or moresensors that measure physical properties, such as temperature, pressure,motion, traffic flow, or other attributes of an object or environment.

FIG. 1 illustrates an example system for generating forecasts based ontime-series data captured by one or more host devices. System 100generally comprises hosts 110 a to 110 n, data collector 120,forecasting services 130, data repository 140, and clients 150 a to 150k. Components of system 100 may be implemented in one or more hostmachines operating within one or more clouds or other networkedenvironments, depending on the particular implementation.

Hosts 110 a to 110 n represent a set of one or more network hosts andgenerally comprise targets 112 a to 112 i and agents 114 a to 114 j. A“target” in this context refers to a resource that serves as a source oftime series data. For example, a target may be a software deploymentsuch as a database server instance, middleware instance, or some othersoftware resource executing on a network host. In addition oralternatively, a target may be a hardware resource, an environmentalcharacteristic, or some other physical resource for which metrics may bemeasured and tracked.

Agents 114 a to 114 j comprise hardware and/or software logic forcapturing time-series measurements from a corresponding target (or setof targets) and sending these metrics to data collector 120. In one ormore embodiments, an agent includes a process, such as a service ordaemon, that executes on a corresponding host machine and monitors oneor more software and/or hardware resources that have been deployed. Inaddition or alternatively, an agent may include one or more hardwaresensors, such as microelectromechanical (MEMs) accelerometers,thermometers, pressure sensors, etc., that capture time-seriesmeasurements of a physical environment and/or resource. Although onlyone agent and target is illustrated per host in FIG. 1, the number ofagents and/or targets per host may vary from implementation toimplementation. Multiple agents may be installed on a given host tomonitor different target sources of time series data. In otherembodiments, an agent that resides remotely on a different host than atarget may be responsible for collecting sample time-series data fromthe target.

Data collector 120 includes logic for aggregating data captured byagents 114 a to 114 j into a set of one or more time-series. Datacollector 120 may store the time series data in data repository 140and/or provide the time-series data to forecasting services 130. In oneor more embodiments, data collector 120 receives data from agents 114 ato 114 j over one or more data communication networks, such as theInternet. Example communication protocols that may be used to transportdata between the components illustrated within system 100 may include,without limitation, the hypertext transfer protocol (HTTP), simplenetwork management protocol (SNMP), and other communication protocols ofthe internet protocol (IP) suite.

Forecasting services 130 includes a forecasting analytic or set ofanalytics that may be invoked to process time-series data. For instance,forecasting services 130 may include logic for detecting and classifyingseasonal behaviors within such as described in U.S. application Ser. No.15/140,358, entitled “SCALABLE TRI-POINT ARBITRATION AND CLUSTERING”;U.S. application Ser. No. 15/057,065, entitled “SYSTEM FOR DETECTING ANDCHARACTERIZING SEASONS”; U.S. application Ser. No. 15/057,060, entitled“SUPERVISED METHOD FOR CLASSIFYING SEASONAL PATTERNS”; and/or U.S.application Ser. No. 15/057,062, entitled “UNSUPERVISED METHOD FORCLASSIFYING SEASONAL PATTERNS”, the entire contents for each of whichwere previously incorporated by reference herein as if set forth intheir entirety. In addition or alternatively, forecasting services 130may include logic for generating forecasts and accommodating statechanges in a forecast, such as described in U.S. Appln. No. 62/301,590,entitled “SEASONAL AWARE METHOD FOR FORECASTING AND CAPACITY PLANNING”;and/or U.S. application Ser. No. 15/266,979, entitled “SYSTEMS ANDMETHODS FOR DETECTING AND ACCOMMODATING STATE CHANGES IN MODELLING”, theentire contents for each of which were previously incorporated byreference herein as if set forth in their entirety.

Data repository 140 includes volatile and/or non-volatile storage forstoring data that is generated and/or used by forecasting services 130.Example data that may be stored may include, without limitation,time-series data collected, seasonal pattern classifications, data pointgroupings, pattern trend rate and intercept data, and forecast data.Data repository 140 may reside on a different host machine, such as astorage server that is physically separate from forecasting services130, or may be allocated from volatile or non-volatile storage on thesame host machine.

Clients 150 a to 150 k represent one or more clients that may accessforecasting services 130 to generate forecasts and/or perform capacityplanning operations. A “client” in this context may be a human user,such as an administrator, a client program, or some other applicationinstance. A client may execute locally on the same host as analyticservices 130 or may execute on a different machine. If executing on adifferent machine, the client may communicate with forecasting services130 via one or more data communication protocols according to aclient-server model, such as by submitting HTTP requests invoking one ormore of the services and receiving HTTP responses comprising resultsgenerated by one or more of the services. Forecasting services 130 mayprovide clients 150 a to 150 k with an interface through which one ormore of the provided services may be invoked. Example interfaces maycomprise, without limitation, a graphical user interface (GUI), anapplication programming interface (API), a command-line interface (CLI)or some other interface that allows a user to interact with and invokeone or more of the provided services.

3. Forecast Analytic Overview

In one or more embodiments, forecasting services 130 receives, as input,a time-series signal and forecasting parameters, such as a start timeand/or duration of the forecast. In response, forecasting services 130outputs a set of forecasted values in accordance with the forecastingparameters. As an example, a client may request a forecast for CPU usageon a given host over the next three months. In response, forecastingservices 130 may analyze a historical set of time-series data thattracks CPU usage on the host. As discussed further herein, the analysismay include, without limitation detecting seasonal patterns within thehistorical set of time-series data and trending the detected seasonalpatterns, if any. Based on the analysis a set of forecasted values theproject CPU usage over the next three months is generated. A chart,graphical interface, or other display may be generated based on theforecasted values to allow a user to quickly visualize the projectedvalues.

Referring to FIG. 2, analytic for generating forecasts based on seasonalpattern trending in accordance with one or more embodiments. Forecastanalytic 200 generally comprises pattern classification logic 210,grouping logic 220, trend rate extraction logic 230, pattern interceptextraction logic 240, and forecasting logic 250. Each logic unit maycomprise hardware and/or software logic to perform a specialized set ofoperations as described further herein. Further, although individuallogic units are shown and described as performing specific operation, insome embodiments, the operations may be merged into a single logic unitor split across multiple logic units.

Pattern detection logic 210 receives, as input, a set of time-seriesdata denoted D, which captures a sequence of values {x₁, . . . xi}.Pattern detection logic 210 processes the set of time-series data D todetect and classify a set of seasonal patterns, denoted P, whichincludes pattern identification information {p1, . . . pj} for eachdetected seasonal pattern. In one or more embodiments, the patternidentification information identifies the different components of aseasonal pattern. A “component” in this context refers to a portion ofthe seasonal pattern that corresponds to a sub-period within theseasonal period. In the context of a weekly high seasonal pattern, forinstance, the components may correspond to the days, hours, or othersub-periods of a week that have been classified as weekly highs. In oneor more embodiments, pattern detection logic 210 may implement thetechniques described in U.S. application Ser. No. 15/140,358, entitled“SCALABLE TRI-POINT ARBITRATION AND CLUSTERING”; U.S. application Ser.No. 15/057,065, entitled “SYSTEM FOR DETECTING AND CHARACTERIZINGSEASONS”; U.S. application Ser. No. 15/057,060, entitled “SUPERVISEDMETHOD FOR CLASSIFYING SEASONAL PATTERNS”; and/or U.S. application Ser.No. 15/057,062, entitled “UNSUPERVISED METHOD FOR CLASSIFYING SEASONALPATTERNS”, to detect and classify seasonal patterns.

Grouping logic 220 receives the set of pattern identificationinformation and, in response, generates, within volatile and/ornon-volatile storage, a set of one or more groups of data points,denoted, G. In one or more embodiments, the data points are grouped byseasonal pattern classification and/or components. As an example, afirst group for seasonal highs may include sample data points fromsamples of different Mondays between 9 and 10 a.m., a second group mayinclude sample data points from the different Mondays between 10 and 11a.m., etc. Thus, a group may correspond to a respective sub-periodwithin a season and comprise data points from different instances of thesub-period.

Trend rate extraction logic 230 receives the set of one or more groupsof data points as input and analyzes the groups according to seasonalpattern classification. Based on the analysis, trend rate extractionlogic 230 generates, within volatile or non-volatile storage, a set ofone or more representative trend rates, denoted T, for the respectiveseasonal patterns that were detected. The representative trend rate forone seasonal pattern may differ from another seasonal pattern dependingon the analysis. For instance, the trend rate for sparse highs may benegative while the trend rate for sparse highs may be positive or viceversa. Thus, the direction and/or magnitude of the trend rate may varybetween different seasonal patterns.

Trend intercept extraction logic 240 also receives the set of one ormore groups of data points as inputs and analyzes the groups accordingto seasonal pattern classification. Based on the analysis, trendintercept extraction logic 240 generates, within volatile ornon-volatile storage, a set of one or more trend intercepts (alsoreferred to as “anchor point”), denoted T, for the respective seasonalpatterns that were detected. The trend intercept in this context refersto the point at which a trend line crosses the y-axis, where the y-axiscorresponds to the values of a metric at the beginning of a seasonalperiod. In the context of resource usages, such as the number of activesessions in a database server, the intercept may correspond to resourceusage at the beginning of a seasonal period. A trend line may be plottedas T_(n)=tx_(n)+i, where T_(n) is the value on a trend line for the nthsample x_(n), t is the representative trend rate for a seasonal pattern,and i is the trend intercept or “anchor point”.

Forecasting logic 250 receives the set of trend rates and trendintercepts as input. Forecasting logic 250 uses the trend rates andintercepts to train a forecasting model and outputs a set of forecastdata denoted F. The forecasting model may trend samples from differentseasonal pattern independently. For example, seasonal highs may betrended independently of seasonal lows, sparse highs may be trendedindependently of dense highs, etc. By analyzing different seasonalpatterns separately, more accurate forecasts may be achieved when theseasonal patterns trend in a different way.

With reference to FIG. 3, an example set of operations for generating aforecast based on seasonal pattern trending is illustrated in accordancewith one or more embodiments. At 302, the process receives a time-seriessignal that includes a sequence of values that measure an attributeassociated with one or more targets over time. For example, thetime-series signal may measure CPU usage, memory bandwidth, databaselogons, active sessions within a database system or other application,and any other hardware or software resource metric.

At 304, the process detects and classifies seasonal patterns within theset of time-series data. For instance, the process may implement thetechniques described in U.S. application Ser. No. 15/140,358, entitled“SCALABLE TRI-POINT ARBITRATION AND CLUSTERING”; U.S. application Ser.No. 15/057,065, entitled “SYSTEM FOR DETECTING AND CHARACTERIZINGSEASONS”; U.S. application Ser. No. 15/057,060, entitled “SUPERVISEDMETHOD FOR CLASSIFYING SEASONAL PATTERNS”; and/or U.S. application Ser.No. 15/057,062, entitled “UNSUPERVISED METHOD FOR CLASSIFYING SEASONALPATTERNS”, to detect and classify seasonal patterns.

At 306, the process groups data point by seasonal pattern and component.A “component” of a seasonal pattern corresponds to a sub-period within aseason that may be independently analyzed. As an example, a componentgroup may organize data points that belong to the same sub-period ofdifferent instances of a week and that are associated with the sameseasonal class. For a given seasonal pattern, a plurality of componentgroupings may be generated, with each group corresponding to andorganizing data points from different sub-periods of a season.

At 308, the process determines representative trend rates by seasonalpattern classification. As will be discussed further below, therepresentative trend rate for a seasonal pattern may be determined,based at least in part, on an analysis of data point pairs within theone or more component groups that are associated with the seasonalpattern. For example, the representative pairwise trend rate may beselected within a median range that is determined from a set of pairwisetrend rates that are computed for the data point pairs.

At 310, the process determines representative trend intercepts byseasonal pattern classification. Similar to the representative trendrate, the representative trend intercept for a seasonal pattern may bedetermined, based at least in part on an analysis of data points withinthe one or more component groups that are associated with the seasonalpattern. For example, the representative intercept may be selectedwithin a median range that is determined from a set of intercepts thatare computed for each data point.

At 312, the process generates forecast data using the representativetrends rates and intercepts for the different seasonal patterns. Theprocess may train a forecasting model to trend samples from differentseasonal pattern independently using the trend rates and interceptsdetermined at 306 and 308, respectively. By trending patternsindependently, the accuracy of forecasted values that are associatedwith each seasonal patter may be improved.

4. Seasonal Pattern Detection and Classification

Seasonal classification logic 210 may analyze seasons of a singleduration or of varying duration to detect seasonal patterns. As anexample, the time-series data may be analyzed for daily patterns, weeklypatterns, monthly patterns, quarterly patterns, yearly patterns, etc.The seasons that are analyzed may be of user-specified duration, apredefined duration, or selected based on a set of criteria or rules. Ifa request received from a client specifies the length of the season as Lperiods, for instance, then seasonal analytic logic 210 analyzes thetime series data to determine whether there are any behaviors that recurevery L periods. If no patterns are detected, then seasonalclassification logic 210 may generate an output to indicate that nopatterns were detected. On the other hand, if seasonal analytic logic210 identifies one or more seasonal patterns, then the detected patternsmay be classified according to techniques described in further detailbelow.

The manner in which seasonal patterns are identified and classified mayvary depending on the particular implementation. Example classificationsmay include, but is not limited to, seasonal highs, seasonal lows,seasonal sparse highs, seasonal sparse, lows, seasonal dense highs, andseasonal dense lows. A feature/pattern is considered sparse if itsduration within a season is less than a threshold thereby indicatingthat the exhibited behavior is an outlier. Sparse features generallymanifest as an isolated data point or as a small set of data points thatare far removed from the average data point within the time-series.Conversely, a feature/pattern may be considered dense if its durationwithin a season satisfies the threshold (e.g., falls within thethreshold or is higher than the threshold), indicating that theexhibited behavior is not an outlier. In some embodiments, a densesignal represents a plurality of instances of time-series data that (1)significantly represents an entire period or sub-period of data and (2)exclude a relatively small portion (e.g., 1%, 5%, or some otherthreshold) of the data as outliers that are not the subject of thefitted signal. A sparse signal may represent data points that areexcluded from the dense class of data points as outliers. For example, adense signal may approximate a seasonal period or sub-period of a timeseries by, for each time increment in the time series, approximating thedata point that is, over multiple historical instances of the timeincrement in multiple historical instances of the time series, average,most likely, most central, has the least average distance, or isotherwise a fit or best fit for the multiple historical instances of thetime increment. In one embodiment, if there is no single data point thatcan approximate, with a certain level of confidence or significance, aparticular time increment, that time increment can be classified as nothaving a dense signal.

There are many possible causes of a sparse signal within a set of timeseries data. As an example, a sparse signal may correspond to a suddensurge (a sparse high) or drop-off (a sparse low) in the usage of aparticular target resource. In some instances, the sparse signal may benoise, such as activity cause by an anomalous event. In other instances,a surge or drop-off may be caused by a recurrent seasonal event, such asa periodic maintenance operation.

For a given set of time series data, a noise signal may have a magnitudethat dominates that of a smaller dense pattern. Without a separatetreatment of sparse and dense features in the time series data, a densepattern may potentially be overlooked due to the magnitude of theoverlaid noise. In order to prevent the dense pattern from goingunclassified, the noise/sparse data may be isolated from the dense datawithin a time series. Separate processing for the sparse and densefeatures of a time series may then be provided when performingclassification and forecasting.

In some embodiments, a time series is decomposed into a noise signal anda dense signal where the noise signal, also referred to herein as asparse signal or sparse component, captures the sparse distribution ofdata in a time series that otherwise has a dense distribution and thedense signal, also referred to herein as the dense component, capturesthe dense distribution of data, removing the noise signal. The manner inwhich a set of time series data is decomposed into a sparse componentand dense component may vary depending on the particular implementation.In some embodiments, the dense component may be obtained from theseasonal factors of an Additive Holt-Winters model. As previouslyindicated, the Holt-Winters model employs triple exponential smoothingto obtain the seasonal index. The applied smoothing, in effect, removesthe sparse component of the original time series signal. The result is atime series that includes the dense features of the original timeseries. While the Additive Holt-Winters model may be used to generate adense signal for a time series, in other embodiments, other techniques,such as other localized averaging or smoothing functions, may be used toobtain the dense signal. Once the dense component has been generated andstored, the noise component may be determined by taking the original setof time series data and subtracting out the dense component from theoriginal signal. The resulting noise signal is a time series thatincludes the noise features from the original time series.

Referring to FIG. 4A, an example set of operations for classifyingseasonal patterns is illustrated in accordance with one or moreembodiments. At 402, the time-series data is preprocessed by generatingblocks of data, where each block of data represents a respectiveinstance of a season within the time series and includes data from thetime series that spans a time period of the seasonal duration. As anexample, if a time series includes data spanning twenty-five weeks andthe length of a season is one week of time, then the time-series datamay be chunked into twenty-five blocks, where the first block includesdata points collected during the first week, the second block datapoints collected during the second week, etc.

At block 404, the process generates, for each block of data, a set ofsub-blocks, where each sub-block of data represents one instance of aseason and includes time-series data spanning a sub-period of aparticular duration. The duration of the sub-period may vary fromimplementation to implementation. As an example, for a weekly season,each sub-period may represent a different hour of time within the week.Thus, a block representing a full week of data may be segmented into onehundred and sixty-eight sub-blocks representing one-hundred andsixty-eight different sub-periods. If a sub-period is defined asrepresenting two hours instead, then a block representing a week may besegmented into eighty-four sub-blocks. As another example, for a monthlyseason, a sub-period may correspond to one day of the month. A blockrepresenting one month may then be segmented into twenty-eight tothirty-one sub-blocks, depending on the number of days in the month.Other sub-periods may also be selected to adjust the manner in whichtime series data are analyzed and summarized.

At 406, the process selects a sub-period of the season to analyze anddetermine how it should be classified. The process may select the firstsub-period of a season and proceed sequentially or select thesub-periods according to any other routine or criteria.

At 408, the process determines whether and how to classify the selectedsub-period of the season based, in part, on the time-series datacollected for one or more instances of the season. In the context wherea particular sub-period represents the first hour of the week, forexample, the process may collect data points from the first hour of eachinstance of the week. If there are twenty-five weeks, then twenty-fivedata points may be collected, with one corresponding to the first hourof each separate week. The process may compare the data pointsrepresenting the first hour of every week against time series data forthe remaining part of the week to determine how to classify theparticular sub-period. If a recurrent pattern is detected, then theprocess continues to block 410. Otherwise the process continues to block412.

At block 410, the process associates the selected sub-period of theseason with a class of seasonal pattern. If a seasonal pattern of highsis detected, for instance, then the instance may be associated with acorresponding class representing recurrent seasonal highs. Similarly,the sub-period may be associated with a class representing recurrentseasonal lows if the process detects a recurrent low pattern from thetime series data within the associated sub-blocks. In other embodiments,the respective instance may be associated with different seasonalpatterns depending on the recurrent patterns detected within thesub-blocks. To associate a sub-period with a particular seasonal class,the process may update a bit corresponding to the sub-period in abit-vector that tracks which sub-periods are associated with theseasonal class.

In some cases, the process may not be able to associate a selectedsub-period with a class of seasonal pattern. This may occur, forinstance, if the sample data points for the corresponding sub-period donot follow a clear recurrent pattern across different seasonal periods.In this scenario, the process may leave the sub-period unclassified.When a sub-period is left unclassified, the process may simply proceedto analyzing the next sub-period of the season, if any, or may update aflag, such as a bit in a bit-vector, that identifies which sub-periodsthe process did not classify in the first pass.

At block 412, the process determines whether there are any remainingsub-periods of the season to analyze for classification. If there is aremaining sub-period of the season to analyze, then the process selectsthe next remaining sub-period of the season and returns to block 406 todetermine how to classify the next sub-period. Otherwise, the processcontinues to block 414.

At block 414, the process returns a set of classification results basedon the analysis performed in the previous blocks. The classificationresults may vary from implementation to implementation and generallycomprise data that identifies how the sub-periods of a season have beenclassified. As an example, for a given sub-period, the classificationresults may identify whether the given sub-period is a sparse high,dense high, a seasonal low, or has been left unclassified. Unclassifiedsub-periods may subsequently be classified based on further analysis.For instance, a homogenization function may be applied to classify thesesub-periods based on how adjacent sub-periods in the season have beenclassified as described in U.S. application Ser. No. 15/057,065,entitled “SYSTEM FOR DETECTING AND CHARACTERIZING SEASONS”.

In some embodiments, the classification of a set of instances may bestored as a set of one or more bit-vectors (also referred to herein asarrays). Referring to FIG. 4B, for instance, it depicts an exampleclassification for instances of a season detected within a set of timeseries data. To obtain the classification results, time series data 420is chunked into a plurality of blocks including 422 a, 422 b, and 422 n,where each block contains data for a different instance of a season.Each of seasonal samples 422 a, 422 b, and 422 n is further chunked intosub-blocks based on the sub-period sample size. Block 422 a is chunkedinto to sub-blocks including data point 424 a, 424 b, and 424 j, block424 b is chunked into sub-blocks containing data point 426 a, 426 b, and426 j, and block 422 i is chunked into sub-blocks containing data point428 a, 428 b, and 428 j. In the context of a weekly season, eachsub-block may represent one week of time series data, and each sub-blockmay contain a data point representing a metric value for a one-hoursub-period within the week. The blocks may represent other seasonaldurations and/or the sub-blocks may represent other sub-periods,depending on the particular implementation.

A set of bit-vectors classify the sub-periods of the season may begenerated based on an analysis of the data points. The bit-vectors thatare illustrated in the present example include bit-vector 430, whichrepresents a first class for seasonal highs, and bit-vector 432, whichrepresents a second class for seasonal lows. Other bit-vectors may alsobe generated to represent different seasonal pattern classificationssuch as sparse high, sparse low, etc., depending on the particularimplementation. Different bits within a bit-vector correspond todifferent sub-periods of a season and act as a Boolean value indicatingwhether the corresponding sub-period is associated with a class or not.For instance, the first seven bits may be set to “1” in bit-vector 430and “0” in bit-vector 432 to indicate that the first seven sub-periodsof the season represent seasonal highs. A subsequent sequence of bitsmay be set to “0” in both bit-vector 430 and bit-vector 432 to indicatethat the corresponding sub-periods of the season are unclassified.Similarly, a subsequent sequence of bits may be set to “0” in bit-vector430 and “1” in bit-vector 432, to indicate that the correspondingsequence of sub-periods of the season are a low season

The length of a bit-vector may vary depending on the number ofsub-periods within a season. In the context of a week-long season, forinstance, bit-vectors 430 and 432 may each store 168 bits representingone hour sub-periods within the season. However, the bit-vectors may beshorter in length when there are fewer sub-periods in a season or longerin length when a greater number of sub-periods are analyzed. This allowsflexibility in the granularity by which sub-periods are analyzed andclassified.

5. Data Point Groupings by Seasonal Pattern and Component

Once data points within the set of time-series data D have beenclassified, grouping logic 220 may leverage the classifications togenerate a set of one or more groups of data points for each seasonalpattern. A group in this context may be generated using a data structurethat organizes and associates data points that have been assigned to thesame group. Example data structures may include, without limitation,linked lists, arrays, hash tables, data point mappings, and treestructures. Grouping data points by seasonal class and componentfacilitates independent processing of seasonal patterns by a computingsystem.

Referring to FIG. 5A an example set of operations for grouping datapoints by seasonal pattern and component are illustrated in accordancewith one or more embodiments. At 502, the process selects a seasonalpattern from the set of seasonal patterns P. For instance, if datapoints have been classified into three separate categories, sparsehighs, dense highs, and lows, the process may select sparse highs or oneof the other seasonal patterns to begin.

At 504, the process selects a component of the seasonal pattern. In theexample where a sparse high is selected, for instance, Mondays from 9a.m. to 12 p.m. may have been classified as sparse highs. In this case,assuming sample rates of an hour, the sparse high would include threeseparate components corresponding to different sub-periods of a season:a first component corresponding to 9 a.m. to 10 a.m., a second componentcorresponding to 10 a.m. to 11 a.m., and a third component correspondingto 11 a.m. to 12 p.m. The process may start by selecting the earliestsub-period or may analyze components in any other order.

At 506, the process identifies sample values for the selected componentacross different instances of a seasonal period. In the example whereMonday at 9 a.m. is selected, the process may identify a sample valuesfor this sub-period across multiple weeks of time-series data. Forexample, if there are four weeks of data where Monday at 9 a.m. has beenclassified as a sparse high, then four sample values may be identifiedand collected for the selected component of the sparse high seasonalpattern.

At 508, the process generates a new component group for the identifiedsample values. As previously mentioned, the group may be a datastructure that organizes, maps, and/or otherwise associates theidentified sample values for the selected component of the seasonalpattern.

At 510, the process determines whether there are any remainingcomponents. In one or more embodiments, the process may analyze the setof pattern identification data in order to determine whether there areremaining components. In the example where the pattern identificationdata indicates that Monday at 9 a.m. to 12 p.m. is a sparse high andMonday at 9 a.m. to 10 a.m. was initially selected, the process mayreturn to 504 and select the next sample (e.g., Monday from 10 a.m. to11 a.m.) that has been classified as a sparse high. The process thenrepeats 506 and 508 for the next component. Once there are no remainingcomponents in the seasonal pattern, the process continues to 512.

At 512, the process determines whether there are any remaining seasonalpatterns. In the example where there are three seasonal patterns (sparsehigh, dense high, and low) and the process begins with the sparse high,the process may then return to 502 and select the seasonal patternclassified as dense high or low to analyze. The process then repeats andgenerates a set of one or more groups of data points for each seasonalpattern. Once there are no remaining seasonal patterns, the processcontinues to 514.

At 514, the process returns handles for the groups that were generatedwithin volatile and/or non-volatile storage. The forecasting analyticmay use the handle to reference and access the groups within memory orother storage during the operations described in further detail below.

FIG. 5B illustrates an example set of grouping results in accordancewith one or more embodiments. Chart 520 depicts an example set oftime-series data that spans three instances (or cycles) of a season. Theperiod of the season may vary depending on the particularimplementation.

Chart 522 depicts an example result of detecting and classifyingseasonal patterns within the set of time series. Specifically, the datapoints that are above the dotted line have been classified as seasonalhighs, and the data points that occur below the dotted line areclassified as seasonal lows.

Chart 524 depicts the results of grouping the data points by seasonalpattern and components. The first four groups, C1, C2, C3, and C4 groupsample data points for the seasonal high pattern. Group C1 groups datapoints from the first sub-period associated with the seasonal pattern,group C2 group data points from the second sub-period, etc. The nextthree groups, C5, C6, and C7, group data points for the seasonal lowpattern. Group C5 groups the first sub-period that has been classifiedas a seasonal low, group C6 the second sub-period, and group C7, thethird.

6. Pattern Trending

Once the data points have been organized by seasonal class andcomponent, trend rate extraction logic 230 and/or trend interceptextraction logic 240 analyzes the groups to generate trend data for theseasonal components and seasonal patterns. In one or more embodiments,trend rate extraction logic 230 generates a representative trend ratefor each seasonal pattern, and trend intercept extraction logic 240generates a representative trend intercept for each seasonal pattern.For instance, if four seasonal patterns have been detected (e.g., sparsehigh, sparse low, dense high, dense low), a separate trend rate andintercept may be computed for each seasonal pattern Thus, samplesassociated with each seasonal pattern may be trended independently.

In order to determine the trend rate and intercept of each seasonalpattern, trend rate extraction logic 230 may perform a pairwise analysisof the sample data points that are associated with each seasonalpattern. In one or more embodiments, a Theil-Sen estimator may beapplied to the data points in order to compute a representative trendrate and intercept. A Theil-Sen estimator in this context computes orapproximates the median slope among all lines through each data pointpair that is associated with a seasonal pattern. The median slope isclassified as the representative tend rate. Once the median slope m hasbeen determined, a line with slope m may be plotted through each datapoint in the seasonal pattern. The representative intercept may then beselected as the median of the intercept values.

As an alternative to the Theil-Sen estimator, which computes the slopefor all possible data point pairings, the set of data point pairs forwhich a slope is computed may be restricted to component groupings. Putanother way, the Theil-Sen estimator considers all unique sample pairswithin a seasonal pattern, while a modified estimator may constrain thepairs to be within the same pattern component such that each pair isseparated by n seasonal periods where n is a positive integer. Oneadvantage of this modification is that instead of getting slopes for alldata point pairs, the process generates a slope across a pattern'scomponents and thereby an estimate of the stability of the patternitself. In addition, because the number of data point pairings for whicha slope is computed is reduced, the processing overhead involved incomputing a representative slope and intercept may also be significantlyreduced.

The grouping and pattern trending techniques further allow for eachseasonal pattern component to be independently analyzed. As an example,a component grouping for Monday, 9 a.m. to 10 a.m. may have slopescomputed for all data point pairs for this sub-period separated by oneor more seasonal cycles. A second component grouping for Monday 10 a.m.to 11 a.m. includes data points for the same seasonal pattern that fallwithin this sub-period. In this example, the data point pairings are notcreated using data points from separate groups to constrain the numberof data point pairs for which slopes are generated. This constraintfacilitates an independent analysis for each component groups of theseasonal pattern. Thus, the trend for the first hour of a seasonalpattern may be compared to the trend of a second seasonal pattern, whichmay be compared to a third hour and so on. In this way, outliers may bequickly identified and processed. The representative slope may then beselected as the median slope of the set of slopes computed for eachgroup in the seasonal pattern.

Referring to FIG. 6A, an example set of operations for determining arepresentative trend rate and intercept for a selected seasonal patternsis illustrated in accordance with one or more embodiments. At 602, theprocess selects a group of data points for a component of the seasonalpattern. As an example, if a seasonal low pattern has componentgroupings for Friday, 11 p.m. to 12 a.m., Saturday, 12 a.m. to 1 a.m.and Sunday, 1 a.m. to 2 a.m., then the process may select the groupcorresponding to the earliest sub-period of a season. However, thecomponents may select the component groups in any order.

At 604, the process selects a data point pair from the group. In theexample where Friday 11 p.m. to 12 a.m. is selected, for instance, thegroup may contain four data points, denoted x₁, x₂, x₃, and x₄ fromthree different weeks. In this scenario, there a six possible data pointpairings:

x₁, x₂;

x₁, x₃;

x₁, x₄;

x₂, x₃;

x₂, x₄; and

x₃, x₄.

The process may select one of the data point pairs in any order andproceed to 606. In other embodiments, the group may contain two, three,or more than four data points, depending on the number of sample valueswithin the set of time-series data that have been assigned to the group.

At 606, the process determines a pairwise trend rate for the data pointpair. The pairwise trend rate may be computed as the slope between thetwo data points. That is, the trend rate for the selected pair may becomputed as follows:

m=(y _(j) −y _(i))/(x _(j) −x _(i))  (9)

where m is the trend rate (or slope), y_(i) is the measured value of thedata point in the data point pair that occurs later in the time-series,y_(j) is the measured value of the data point in the data point pairthat occurs earlier in the time-series, x_(j) represents the a samplenumber, time, or position within the time series for the data point thatoccurs later in the time series, and x_(i) represents the a samplenumber, time, or position within the time series for the data point thatoccurs earlier in the time series. Once the pairwise trend rate has beencomputed, it may be stored in a data structure that groups pairwisetrends rates for the seasonal component.

At 608, the process determines whether there are any remaining datapoint pairs. If there are, then the process returns to 604 and isrepeated for each of the remaining data point pairs. Once a set ofslopes has been generated and stored for each data point pair in thegroup, the process continues to 610.

At 610, the process determines whether there are any remaining groups toanalyze for the seasonal pattern. If so, then the process returns to 602and generates a set of pairwise trend slopes for each remaining seasonalcomponent. Each seasonal component may be analyzed independently suchthat data points from different groups are not paired. This reduces thenumber of data point pairs for which trend information is generated incomparison to a Thiel-Sen estimator. It also allows the trend ofindividual seasonal components to be analyzed independently to estimateof the stability of the pattern itself

At 612, a representative trend rate for the seasonal pattern isdetermined by analyzing the set of trend rates for each of the componentgroupings and selecting the median trend rate. For example, if a set ofslopes includes ten values sorted from lowest to highest, the medianwould be the sum of the two middle slope values divided by two. In a setwith eleven values, the median would be the middle slope value.

At 614, a representative trend intercept for the seasonal pattern isdetermined based, at least in part, using the representative trend rate.To determine a representative trend intercept for a particular seasonalpattern, the process may determine an intercept for each data pointassociated with the seasonal pattern as follows:

b=(y _(i) −t _(s) x _(i))  (10)

where b is the intercept, y_(i) is the measured value for the data pointfor which the intercept is being computed, t_(s) is the representativetrend rate for the seasonal pattern, and x_(j) represents the samplenumber, time, or position of the data point within the time-series. Therepresentative trend intercept for the seasonal pattern may then beselected as the median intercept in the set of intercepts.

By selecting the median as a representative value, outlier slopes andintercepts may be eliminated and prevented from influencing the modelledtrend of the seasonal pattern. By contrast, using an average valueallows extremely large or small trend rates and intercepts, caused bydata point outliers, to skew the trend rate up or down. Once therepresentative trend rate and intercept have been determined for aseasonal pattern, the process may repeat for other seasonal patterns todetermine corresponding trend rates and intercepts/anchor points. Thus,the process may be used to compute a representative trend rate andintercept for each distinct seasonal pattern that was detected.

In one or more embodiments, rather than selecting the exact median trendrate and intercept, a median range may be defined. For example, a medianrange may be defined such that a slope or intercept within a predefinedthreshold in proximity to the middle value (or middle values) may beselected instead as the representative value. In the set with elevenvalues, for instance, the two values adjacent to the middle value may beselected instead or averaged together to compute the representativetrend rate. Thus, there are many different ways in which therepresentative trend rate may be determined based on the median.

FIG. 6B illustrate an example set of results for selecting arepresentative trend rate and intercept for different seasonal patternsin accordance with one or more embodiments. Chart 620 depictsconnections between the data point pairs within groups C1 to C7. As canbe seen, each group includes three data points that are used to formthree separate data point pairs.

Chart 622 plots the pairwise slope distribution for data point pairswithin the seasonal high groups C1 to C4, and chart 624 plots thepairwise slope distribution for data point pairs within the seasonal lowgroups C5 to C7. The line m in each respective chart indicates themedian slope for the different seasonal patterns. As can be seen, themedian slope for the seasonal highs is different than the median slopefor the seasonal lows. In other words, a different representative trendrate is selected for each respective seasonal pattern.

Chart 626 displays the trend intercept distribution for data pointswithin the seasonal high groups C1 to C4, and chart 628 displays theintercept distribution for data points within the seasonal low componentgroups C5 to C7. As can be seen, the median intercepts for the seasonalhighs differs from the median intercept for the seasonal lows. Theserepresentative intercepts may be used to trend the seasonal highsindependently of the seasonal lows.

7. Temporally Weighted Pattern Trending

In one or more embodiments, the techniques for pattern trendingpreviously described may apply temporal weighting to data point pairs.With temporal weighting, data point pairs that are more recent are givengreater weight/influence toward determining the representative trendrate than data point pairs that occur earlier in the time-series. Inparticular, the individual pairwise slope and intercept estimates areweighted by terms that are inferred from the cycle (number of periods).

Referring to FIG. 7A, an example set of operations for trending patternsusing temporal weighting is illustrated in accordance with one or moreembodiments. At 702 a weight is assigned to each sample data point thatis being used to train a forecasting model. In one or more embodiments,the weight is assigned as a function of the cycle in which the sampledata point is found. For example, the weight may be assigned as follows:

w=(c/n _(c))  (11)

where w is the weight value for the sample, c is the cycle that thesample is in and n_(c) is the number of cycles used to train theforecasting model.

With reference to FIG. 7B, for example, table 730 stores a mappingbetween samples, seasonal pattern classifiers, and assigned weights. Inthis example there are three cycles—data points from the first seasonalcycle (e.g., the first week) are assigned a weight of 0.33, data pointsfrom the second seasonal cycle (e.g., the second week) are assigned aweight of 0.67, and data points from the third seasonal cycle (e.g., thethird week) are assigned a weight of 1. Thus, data points from the mostrecent instance of a seasonal period are given more weight than datapoints in earlier instances.

Returning to FIG. 7A, at 704, the process determines inner grouppair-wise trend rates. The trend rates may be computed/generatedaccording to the techniques previously described using equations (9)above.

At 706, the pairwise slopes are sorted for each seasonal pattern. Forexample, a first set of pairwise slopes may be sorted for a sparse highseason, a second for a dense high, a third for a dense low, etc. Theslopes may be sorted, within volatiles and/or non-volatiles storage,from low to high or high to low, depending on the particularimplementation.

At 708, weights are determined for the pairwise slopes based on theweights of the data point pairs. In one or more embodiments, the processdetermines an initial weight by multiplying the weight of each datapoint in the pair together. This weight may then be normalized bydividing the assigned weight value by the sum of all weights in the setof pairwise slopes for the seasonal pattern.

At 710, the process calculates a cumulative weight for each seasonalpattern. The cumulative weight may be obtained by summing the normalizedweights together.

At 712, a representative trend rate is determined for each respectiveseasonal pattern based, at least in part, on the cumulative weightassociated with each seasonal pattern. For example, the representativetrend rate may be generated by interpolating to find the point at whichthe weights of the pairwise slopes are balanced. In one or moreembodiments, the representative trend rate is the slope which isapproximately fifty percent (or within a threshold range of fiftypercent) of the cumulative total weight. In other words, the weightedmedian slope may be classified as the representative trend rate for thecorresponding seasonal pattern.

Referring again to FIG. 7B, table 732 stores, for the seasonal highpattern, a mapping between data point pairs and their weighted slopesbefore normalization. The assigned weight is computed by multiplying theweights of each respective data point in the data point pair together.Thus, the data point pair “1, 5” has a weight of 0.33 (assigned tosample “1”)×0.67 (assigned to sample “5”) which is approximately 0.22.

Table 736 stores, for the seasonal low pattern, a mapping betweenassociated data point pairs and their weighted slopes beforenormalization. As above for the seasonal high data points, the pairwisetrend weights in table 736 are computed by multiplying the weightsassigned to each individual data point in the respective data pointpair.

Table 734 depicts an example mapping between the sorted pairwise slopesfor the seasonal high pattern, their initially assigned weights, theirnormalized weights, and the cumulative total. As can be seen, thecumulative total is aggregated from low to high. The representativeweight for the seasonal highs is 0.20, which is the point where thenormalized weights are balanced (50% of cumulative total).

Table 738 depicts an example mapping between the sorted pairwise slopesfor the seasonal low pattern, their initially assigned weights, theirnormalized weights, and the cumulative total. The representative weightfor the seasonal lows is −0.05, which is the point where the normalizedweights are balanced (50% of cumulative total).

Once assigned to a seasonal pattern, the representative slope may thenbe used to determine a representative intercept. Referring again to FIG.7A, at 714, the process determines a set of weighted intercepts for eachseasonal pattern. The intercept for a given data point may be computedaccording to equation (10) above using the representative trend rate forthe seasonal pattern. The weights that are assigned to each intercept inthis case is the weight of the data point used to compute the intercept.

At 716, the process sorts the weighted intercepts for each seasonalpattern. For example, a first set of intercepts may be sorted for asparse high season, a second for a dense high, a third for a dense low,etc. The intercepts may be sorted, within volatiles and/or non-volatilesstorage, from low to high or high to low, depending on the particularimplementation.

At 718, the weights of the intercepts are normalized. In one or moreembodiments, the weight of an intercept is normalized by dividing theweight by the sum of all weights assigned to intercepts in the sortedset of intercepts for each seasonal pattern.

At 720, the process calculates a cumulative weight for each seasonalpattern. The cumulative weight may be obtained by summing the normalizedweights for the intercepts together.

At 722, the process determines a representative intercept for eachseasonal pattern based on the cumulative weights computed for eachseasonal pattern. For example, the representative trend intercept may begenerated by interpolating to find the point at which the weights of theintercepts are balanced. In one or more embodiments, the representativeintercept is the intercept which is approximately fifty percent (orwithin a threshold range of fifty percent) of the cumulative totalweight. In other words, the weighted median intercept may be classifiedas the representative intercept for the corresponding seasonal pattern.

Referring again to FIG. 7B, table 740 stores, for the seasonal highpattern, a mapping between data points, and their weighted interceptsbefore normalization. The assigned intercept weight is the same weightas the data point used to compute the intercept. Thus, the interceptcomputed using the first sample data point has a weight of 0.33 sincethe sample is from the first cycle of the time-series.

Table 742 depicts an example mapping between the sorted intercepts forthe seasonal high pattern, their initially assigned weights, theirnormalized weights, and the cumulative total. As can be seen, thecumulative total is aggregated from low to high. The representativeintercept for the seasonal highs is 113, which is the point where thenormalized weights are balanced (50% of cumulative total).

Table 744 stores, for the seasonal low pattern, a mapping between datapoints, and their weighted intercepts before normalization. As above forthe seasonal high data points, the intercepts weights are the same asthe data points used to compute the intercept.

Table 748 depicts an example mapping between the sorted intercepts forthe seasonal low pattern, their initially assigned weights, theirnormalized weights, and the cumulative total. The representativeintercept for the seasonal lows is 17.5, which is the point where thenormalized weights are balanced (50% of cumulative total).

8. Forecast Generation

Forecasting logic 250 performs seasonal forecasting based on theseasonal characteristics associated with an input set of time seriesdata, including the pattern trending previously discussed. In one ormore embodiments, in addition to the set of trend rates T and the set oftrend intercepts I, forecasting logic 250 may further receive as input,the set of time-series data D, the set of seasonal patternidentification data P, and a horizon identifying how far past the end ofthe time series to generate forecasted values. Forecasting logic 250process the inputs to generate a forecast that begins at the end of theinput time series and progresses up to the specified horizon. If aclient requests a forecast for an n week horizon, for instance,forecasting logic 250 may generate the set of forecast data F thatincludes projected values for n weeks past the end time of the inputtime series. The horizon may be specified as a particular date or as astretch of time in terms of hours, days, months, etc.

Referring to FIG. 7A, an example set of operations for generating aforecast using different trends rates and intercepts for differentseasonal patterns is depicted in accordance with one or moreembodiments. At block 802, the process identifies a sequent ofsub-periods for which to generate projected values. For example, if aclient has requested a forecast that projects values one week into thefuture with a sample rate of one hour sub-periods, the process mayidentify 168 different sub-periods corresponding to different hourswithin the week. The number of sub-periods may vary from implementationto implementation depending on the length of the requested forecast andthe sample sub-period duration.

At 804, the process selects a sub-period for which to generate aprojected value. For instance, the process may start at the firstsub-period from the end of the input time series and continue toward theend of the forecast horizon. In the context of a one week forecast, forexample, the first sub-period may be the first hour of the week or thefirst hour from the time the forecast is requested. The process may thenproceed to generate forecasted values for each subsequent hour until theend of the week is reached.

At 806, the process determines the seasonal pattern that is associatedwith the selected sub-period. As an example, if the selected sub-periodcorresponds to Monday, 9-10, then the process may determine whether thesub-period has been classified as a sparse high, dense high, sparse low,dense low, or some other pattern classification.

At 808, the process generates a projected value based on therepresentative trend rate and intercept for the associated seasonalpattern. In the context where values are grouped into a sparse highclass, a high class, and a low class, the forecasted value atsample/sub-period (t) may be calculated as follows:

-   -   If t maps to a sparse high, then

F _(t)=SF_(t)+TR_SH_(t−i)+A_SH  (12)

If t maps to a high, then

F _(t)=SF_(t)+TR_H_(t−i)+A_H  (13)

Otherwise

F _(t)=SF_(t)+TR_NH_(t−i)+A_NH  (14)

where F_(t) represents the forecast value for the sample at the givensub-period/time, SF_(t) is the seasonal factor for that sub-period,TR_SH_(t−i)/TR_H_(t−1)/TR_NH_(t−i) represent the trend rate for sparsehigh, high and not high, respectively, i represents the end time of theinput time series, and A_SH/A_H/A_NH represent the anchor points forsparse high, high and not high, respectively.

At block 810, the process determines whether there are remainingsub-periods for which to generate forecasted values. If the horizon hasnot been reached, then the process returns to 804 and selects the nextsub-period in the sequence. The process then computes the forecastedvalue for the next sub-period based on how the corresponding sub-periodhas been classified. If there are no remaining sub-periods in thesequence, then the process continues to block 812.

At 812, the process stores, displays, and/or otherwise outputs theprojected values in the forecast. For example, a graph, chart, or otherdisplay may be generated that combines observed values from one or moreobserved seasonal periods within the time series with projected valuesfor one or more future seasonal periods for which no observed data hasbeen collected. The projected values for the different seasonal classesmay be stitched together or otherwise combined into a single plot orother graphic to provide an overall forecast and/or may be isolated intoseparate graphics.

FIG. 8B illustrates a difference in forecasts between sample trendingand pattern trending in accordance with one or more embodiments. Chart820 displays example forecast results when samples are trended. The line822 indicates a “tipping point” as described in U.S. application Ser.No. 15/266,979, entitled “SYSTEMS AND METHODS FOR DETECTING ANDACCOMMODATING STATE CHANGES IN MODELLING”. Time-series data before line822 is ignored when training the forecasting model. By trending based onwhere data points fall within a sample week period, a negative trend isinferred in the sparse highs. This negative trend is inferred because inthe small set of data used to training the forecasting model, sparsehighs occur earlier in the week. An unsupervised seasonalityclassification model may sometimes select lower values that occur laterin the week as highs, pulling down the trend rate and leading toinaccurate forecast results for the sparse high pattern. If the sparsehighs had occurred later in the week, then a large positive trend may beincorrectly inferred. Thus, by trending on the sample rather than thepattern, the location of data points within the sample may significantlyaffect the trend rate calculation.

Chart 830 displays an example forecast where pairwise trend slopes andintercepts are used to trend the patterns. Once again, line 832indicates the tipping point, and data before this time is not used totrain the forecasting model. As can be seen, the sparse highs in thisinstance are relatively stable. Thus, using pairwise trend slopesanalyzes the overall trend of the pattern rather than where data pointsoccur within an arbitrary window of time within a season. This allowsmore accurate forecasts to be generated for the time-series data andseasonal patterns therein.

9. Forecast Uncertainty Based on Seasonal Pattern Classifications

In one or more embodiments, forecasting logic 250 determines a set ofone or more uncertainty values for a given forecast. The uncertaintyvalues may include residuals, confidence intervals, projectionintervals, and/or tolerance intervals depending on the particularimplementation.

A tolerance interval models uncertainty in a way that allows the user tounderstand whether or not the system has a significant likelihood ofexceeding a tolerance. Confidence intervals, which may also be computedfor a forecasting model, differ in that the confidence interval is usedto indicate an interval where the average value or variance within aforecast is expected to fall. By contrast, the tolerance interval isused to indicate a range where an individual forecasted value isexpected to fall. In other words a tolerance interval may bemathematically defined to be the range of values that will contain athreshold percentage of future samples. The confidence interval's widthis based on the sampling error and is generally narrower than thetolerance interval's width, which is based both on the sampling errorand the variance in values.

The tolerance interval for a prescribed confidence of γ may defined tobe x±λs such that

$\begin{matrix}{{{\frac{1}{\sqrt{2\pi \; \sigma^{2}}}{\int_{\overset{\_}{x} - {\lambda \; s}}^{\overset{\_}{x} + {\lambda \; s}}{e^{{{- {({t - \mu})}^{2}}/2}\sigma^{2}}{dt}}}} \geq \gamma};} & (15)\end{matrix}$

where x is the sample mean, s² is the sample variance, σ is the standarddeviation, and t is the sample time.

In some cases, the tolerance interval may be focuses on the standardnormal distribution without loss of generality. As a result, thetolerance interval can also be defined to be x+λs such that

$\begin{matrix}{{\frac{1}{\sqrt{2\pi}}{\int_{\overset{\_}{x} - {\lambda \; s}}^{\overset{\_}{x} + {\lambda \; s}}{e^{{- t^{2}}/2}{dt}}}} \geq \gamma} & (16)\end{matrix}$

The integral statement of Eq. 13 translates to a statement where λs≧rwith r being the root of

${\frac{1}{\sqrt{2\pi}}{\int_{\overset{\_}{x} - r}^{\overset{\_}{x} + r}{e^{{- t^{2}}/2}{dt}}}} = {\gamma.}$

Upon further analysis, λs≧r may be rewritten as

${\left( {n - 1} \right)s^{2}} \geq {\frac{\left( {n - 1} \right)r^{2}}{\lambda^{2}}.}$

The reason for this modification is that for the standard normaldistribution, (n−1)s² has a chi-squared distribution with n−1 degrees offreedom. If the confidence of the fit is equal to the confidence of thetolerance interval (i.e. β=γ) then this results in the following:

$\begin{matrix}{\chi_{{n - 1},\gamma}^{2} \geq {\left( {n - 1} \right)s^{2}} \geq \frac{\left( {n - 1} \right)r^{2}}{\lambda^{2}}} & (17)\end{matrix}$

With further analysis, it may be determined that

$\lambda \geq \sqrt{\frac{\left( {n - 1} \right)r^{2}}{\chi_{{n - 1},\gamma}^{2}}}$

and as a result, the following equation derived:

$\begin{matrix}{r^{2} \approx {\left( {1 + \frac{1}{n}} \right){z_{{({1 - \gamma})}/2}^{2}.}}} & (18)\end{matrix}$

As with the projected values described above, uncertainty values may bederived based in part on the seasonality analytics applied to a set oftime series.

In an embodiment, the forecast high and low are generated by adding orsubtracting, respectively, the uncertainty from the forecasted value.For instance the following equations may be used to compute the forecasthigh and low for sample sub-period t:

If t maps to a sparse high, then

FH_(t) =F _(t) +USH  (19)

FL_(t) =F _(t) −USH  (20)

If t maps to a high, then

FH_(t) =F _(t) +UH  (21)

FL_(t) =F _(t) −UH  (22)

Otherwise

FH_(t) =F _(t) +UNH  (23)

FL_(t) =F _(t) −UNH  (24)

where FH_(t) is the forecast high value, FL_(t) is the forecast lowvalue, F_(t) is the projected forecast value, USH is the sparse highuncertainty computed from the residuals from the sparse high class, UHis the high uncertainty computed from the residuals from the high class,and UNH is the uncertainty computed from the residuals from samples thatwere not classified as seasonal highs (sparse or dense).

10. Seasonally-Aware Capacity Planning

Seasonal forecasting may be used to facilitate and/or automaticallyperform capacity planning decisions and operations, according to one ormore embodiments. Underestimating future resource usage may lead tosignificant decreases in performance if the deployed resources areoverloaded. With a separate treatment of sparse highs from dense highsand lows, as previously described, the impact of low usage periods onthe forecast may be mitigated, thereby reducing the likelihood that peakresource usage parameters will be underestimated.

In an embodiment, the projected values may be used to plan, deploy,recommend, and/or order resources to handle increased resource usage.Different actions and/or recommendations may be set to trigger upondetecting that a projected value or trend exceeds a threshold. As anexample, the projected sparse high values may indicate that resourceusage will exceed a threshold thereby overloading current resources at afuture time. In response, the system may recommend additional hardwareand/or software resources to satisfy the projected increase in resourceusages.

In another embodiment, the projected values may be used to consolidateresources. For instance, if resource usage is projected to decline pasta threshold, then the system may recommend or automatically consolidatehardware and/or software resources to more efficiently utilize theseresources and free up resources for other applications.

Based on a seasonal forecast, administrators may determine a variety ofcharacteristics associated with a particular resource or set ofresources. For instance, the forecast may indicate whether there is ahigh risk of exhaustion for the resource, a high risk for exhaustion forbatch (sparse) jobs but low risk for typical (dense) workloads, a lowrisk for exhaustion but increasing trend, a consistent, predictablescheduled load, a decreasing trend in load, etc. In the context of aclustered database that is distributed across multiple hosts, a user maydetermine if the system or any instance is likely to run out of capacitywithin the next 30 days (or some other horizon). The user may alsodetermine if the load for two or more applications may be handled by asingle database instance.

11. Hardware Overview

According to one embodiment, the techniques described herein areimplemented by one or more special-purpose computing devices. Thespecial-purpose computing devices may be hard-wired to perform thetechniques, or may include digital electronic devices such as one ormore application-specific integrated circuits (ASICs) or fieldprogrammable gate arrays (FPGAs) that are persistently programmed toperform the techniques, or may include one or more general purposehardware processors programmed to perform the techniques pursuant toprogram instructions in firmware, memory, other storage, or acombination. Such special-purpose computing devices may also combinecustom hard-wired logic, ASICs, or FPGAs with custom programming toaccomplish the techniques. The special-purpose computing devices may bedesktop computer systems, portable computer systems, handheld devices,networking devices or any other device that incorporates hard-wiredand/or program logic to implement the techniques.

For example, FIG. 9 is a block diagram that illustrates computer system900 upon which one or more embodiments may be implemented. Computersystem 900 includes bus 902 or other communication mechanism forcommunicating information, and hardware processor 904 coupled with bus902 for processing information. Hardware processor 904 may be, forexample, a general purpose microprocessor.

Computer system 900 also includes main memory 906, such as a randomaccess memory (RAM) or other dynamic storage device, coupled to bus 902for storing information and instructions to be executed by processor904. Main memory 906 also may be used for storing temporary variables orother intermediate information during execution of instructions to beexecuted by processor 904. Such instructions, when stored innon-transitory storage media accessible to processor 904, rendercomputer system 900 into a special-purpose machine that is customized toperform the operations specified in the instructions.

Computer system 900 further includes read only memory (ROM) 908 or otherstatic storage device coupled to bus 902 for storing static informationand instructions for processor 904. Storage device 910, such as amagnetic disk or optical disk, is provided and coupled to bus 902 forstoring information and instructions.

Computer system 900 may be coupled via bus 902 to display 912, such as acathode ray tube (CRT), liquid crystal display (LCD), or light-emittingdiode (LED), for displaying information to a computer user. Input device914, which may include physical and/or touchscreen based alphanumerickeys, is coupled to bus 902 for communicating information and commandselections to processor 904. Another type of user input device is cursorcontrol 916, such as a mouse, a trackball, or cursor direction keys forcommunicating direction information and command selections to processor904 and for controlling cursor movement on display 912. This inputdevice typically has two degrees of freedom in two axes, a first axis(e.g., x) and a second axis (e.g., y), that allows the device to specifypositions in a plane.

Computer system 900 may implement the techniques described herein usingcustomized hard-wired logic, one or more ASICs or FPGAs, firmware and/orprogram logic which in combination with the computer system causes orprograms computer system 900 to be a special-purpose machine. Accordingto one embodiment, the techniques herein are performed by computersystem 900 in response to processor 904 executing one or more sequencesof one or more instructions contained in main memory 906. Suchinstructions may be read into main memory 906 from another storagemedium, such as storage device 910. Execution of the sequences ofinstructions contained in main memory 906 causes processor 904 toperform the process steps described herein. In alternative embodiments,hard-wired circuitry may be used in place of or in combination withsoftware instructions.

The term “storage media” as used herein refers to any non-transitorymedia that store data and/or instructions that cause a machine tooperation in a specific fashion. Such storage media may comprisenon-volatile media and/or volatile media. Non-volatile media includes,for example, optical or magnetic disks, such as storage device 910.Volatile media includes dynamic memory, such as main memory 906. Commonforms of storage media include, for example, a floppy disk, a flexibledisk, hard disk, solid state drive, magnetic tape, or any other magneticdata storage medium, a CD-ROM, any other optical data storage medium,any physical medium with patterns of holes, a RAM, a PROM, and EPROM, aFLASH-EPROM, NVRAM, any other memory chip or cartridge.

Storage media is distinct from but may be used in conjunction withtransmission media. Transmission media participates in transferringinformation between storage media. For example, transmission mediaincludes coaxial cables, copper wire and fiber optics, including thewires that comprise bus 902. Transmission media can also take the formof acoustic or light waves, such as those generated during radio-waveand infra-red data communications.

Various forms of media may be involved in carrying one or more sequencesof one or more instructions to processor 904 for execution. For example,the instructions may initially be carried on a magnetic disk or solidstate drive of a remote computer. The remote computer can load theinstructions into its dynamic memory and send the instructions over atelephone line using a modem. A modem local to computer system 900 canreceive the data on the telephone line and use an infra-red transmitterto convert the data to an infra-red signal. An infra-red detector canreceive the data carried in the infra-red signal and appropriatecircuitry can place the data on bus 902. Bus 902 carries the data tomain memory 906, from which processor 904 retrieves and executes theinstructions. The instructions received by main memory 906 mayoptionally be stored on storage device 910 either before or afterexecution by processor 904.

Computer system 900 also includes a communication interface 918 coupledto bus 902. Communication interface 918 provides a two-way datacommunication coupling to a network link 920 that is connected to localnetwork 922. For example, communication interface 918 may be anintegrated services digital network (ISDN) card, cable modem, satellitemodem, or a modem to provide a data communication connection to acorresponding type of telephone line. As another example, communicationinterface 918 may be a local area network (LAN) card to provide a datacommunication connection to a compatible LAN. Wireless links may also beimplemented. In any such implementation, communication interface 918sends and receives electrical, electromagnetic or optical signals thatcarry digital data streams representing various types of information.

Network link 920 typically provides data communication through one ormore networks to other data devices. For example, network link 920 mayprovide a connection through local network 922 to host computer 924 orto data equipment operated by Internet Service Provider (ISP) 926. ISP926 in turn provides data communication services through the world widepacket data communication network now commonly referred to as the“Internet” 928. Local network 922 and Internet 928 both use electrical,electromagnetic or optical signals that carry digital data streams. Thesignals through the various networks and the signals on network link 920and through communication interface 918, which carry the digital data toand from computer system 900, are example forms of transmission media.

Computer system 900 can send messages and receive data, includingprogram code, through the network(s), network link 920 and communicationinterface 918. In the Internet example, server 930 might transmit arequested code for an application program through Internet 928, ISP 926,local network 922 and communication interface 918.

The received code may be executed by processor 904 as it is received,and/or stored in storage device 910, or other non-volatile storage forlater execution.

12. Miscellaneous; Extensions

Embodiments are directed to a system with one or more devices thatinclude a hardware processor and that are configured to perform any ofthe operations described herein and/or recited in any of the claimsbelow.

In an embodiment, a non-transitory computer readable storage mediumcomprises instructions which, when executed by one or more hardwareprocessors, causes performance of any of the operations described hereinand/or recited in any of the claims.

Any combination of the features and functionalities described herein maybe used in accordance with one or more embodiments. In the foregoingspecification, embodiments have been described with reference tonumerous specific details that may vary from implementation toimplementation. The specification and drawings are, accordingly, to beregarded in an illustrative rather than a restrictive sense. The soleand exclusive indicator of the scope of the invention, and what isintended by the applicants to be the scope of the invention, is theliteral and equivalent scope of the set of claims that issue from thisapplication, in the specific form in which such claims issue, includingany subsequent correction.

What is claimed is:
 1. A method comprising: generating, within at leastone of volatile or non-volatile storage for a particular seasonalpattern detected within a set of time-series data, a set of one or moregroups of data points that are associated with the particular seasonalpattern; determining a set of pairwise slopes for data point pairswithin the set of one or more groups of data points; determining, basedat least in part on the plurality of pairwise slopes, a representativetrend rate for the particular seasonal pattern; and generating, withinat least one of volatile or non-volatile storage, a set of forecastedvalues for the particular seasonal pattern based, at least in part, onthe representative trend rate for the particular seasonal pattern. 2.The method of claim 1, wherein determining, based at least in part onthe plurality of pairwise slopes a representative trend rate for theparticular seasonal pattern comprises classifying at least one slopevalue that approximates a median of the set of pairwise slopes for datapoint pairs within the set of one or more groups of data points as therepresentative trend rate for the particular seasonal pattern.
 3. Themethod of claim 1, further comprising: determining, using therepresentative trend rate for the particular seasonal pattern, a set ofintercept values for data points that are associated with the particularseasonal pattern; determining, based at least in part on the set ofintercept values, a representative intercept for a trend of theparticular seasonal pattern; wherein the set of forecasted values isfurther generated based, at least in part, on the representativeintercept.
 4. The method of claim 3, wherein the representativeintercept is at least one median intercept value in the set of interceptvalues.
 5. The method of claim 1, wherein the particular seasonalpattern is a first seasonal pattern and the representative trend rate isa first representative trend rate, the method further comprising:determining, based on at least a second set of pairwise slopes, a secondrepresentative trend rate for a second seasonal pattern detected withinthe set of time-series data; and generating, within at least one ofvolatile or non-volatile storage, a second set of forecasted values forthe second seasonal pattern based, at least in part, on the secondrepresentative trend rate for the second seasonal pattern; wherein thesecond representative trend rate is different than the firstrepresentative trend rate.
 6. The method of claim 1, wherein the set ofone or more groups of data points comprises a plurality of groupsincluding a first group and a second group; wherein the first groupincludes a first set of data points from a first sub-period of multipleinstances of a seasonal period and the second group includes a secondset of data points from a second sub-period of multiple instances of theseasonal period; wherein the set of pairwise slopes includes a firstsorted group of pairwise slopes that are determined for data point pairsformed from data points in the first set of data points and a secondsorted group of pairwise slopes that are determined for data point pairsformed from the second set of data points.
 7. The method of claim 6,wherein the first set of data points are sample values from a first hourof different instances of a week; wherein the second set of data pointsare sample values from a second hour the different instances of theweek; wherein the first hour is different than the second hour.
 8. Themethod of claim 1, further comprising: assigning a respective weight toeach respective data point in set of one or more data point groups;wherein data points that are from a more recent seasonal cycle are givena greater weight than data points that are from a less recent seasonalcycle; and determining a temporal weight for each respective pairwiseslope in the set of pairwise slopes based on the respective weightassigned to each respective data point in a data point pair used tocompute the respective pairwise slope.
 9. The method of claim 8, whereinthe representative trend rate is a weighted median that is determinedbased, at least in part, on the temporal weight for each pairwise slope.10. The method of claim 1, wherein the particular seasonal pattern isone of a sparse seasonal high, a dense seasonal high, a dense seasonallow, or a sparse seasonal low.
 11. One or more non-transitorycomputer-readable media storing instructions, which when executed by oneor more hardware processors, cause operations comprising: generating,within at least one of volatile or non-volatile storage for a particularseasonal pattern detected within a set of time-series data, a set of oneor more groups of data points that are associated with the particularseasonal pattern; determining a set of pairwise slopes for data pointpairs within the set of one or more groups of data points; determining,based at least in part on the plurality of pairwise slopes, arepresentative trend rate for the particular seasonal pattern; andgenerating, within at least one of volatile or non-volatile storage, aset of forecasted values for the particular seasonal pattern based, atleast in part, on the representative trend rate for the particularseasonal pattern.
 12. The one or more non-transitory computer-readablemedia of claim 11, wherein instructions for determining, based at leastin part on the plurality of pairwise slopes a representative trend ratefor the particular seasonal pattern comprise instructions forclassifying at least one slope value that approximates a median of theset of pairwise slopes for data point pairs within the set of one ormore groups of data points as the representative trend rate for theparticular seasonal pattern.
 13. The one or more non-transitorycomputer-readable media of claim 11, wherein the instructions furthercause operations comprising: determining, using the representative trendrate for the particular seasonal pattern, a set of intercept values fordata points that are associated with the particular seasonal pattern;determining, based at least in part on the set of intercept values, arepresentative intercept for a trend of the particular seasonal pattern;wherein the set of forecasted values is further generated based, atleast in part, on the representative intercept.
 14. The one or morenon-transitory computer-readable media of claim 13, wherein therepresentative intercept is at least one median intercept value in theset of intercept values.
 15. The one or more non-transitorycomputer-readable media of claim 11, wherein the particular seasonalpattern is a first seasonal pattern and the representative trend rate isa first representative trend rate, the instructions further causingoperations comprising: determining, based on at least a second set ofpairwise slopes, a second representative trend rate for a secondseasonal pattern detected within the set of time-series data; andgenerating, within at least one of volatile or non-volatile storage, asecond set of forecasted values for the second seasonal pattern based,at least in part, on the second representative trend rate for the secondseasonal pattern; wherein the second representative trend rate isdifferent than the first representative trend rate.
 16. The one or morenon-transitory computer-readable media of claim 11, wherein the set ofone or more groups of data points comprises a plurality of groupsincluding a first group and a second group; wherein the first groupincludes a first set of data points from a first sub-period of multipleinstances of a seasonal period and the second group includes a secondset of data points from a second sub-period of multiple instances of theseasonal period; wherein the set of pairwise slopes includes a firstsorted group of pairwise slopes that are determined for data point pairsformed from data points in the first set of data points and a secondsorted group of pairwise slopes that are determined for data point pairsformed from the second set of data points.
 17. The one or morenon-transitory computer-readable media of claim 16, wherein the firstset of data points are sample values from a first hour of differentinstances of a week; wherein the second set of data points are samplevalues from a second hour the different instances of the week; whereinthe first hour is different than the second hour.
 18. The one or morenon-transitory computer-readable media of claim 11, the instructionsfurther causing operations comprising: assigning a respective weight toeach respective data point in set of one or more data point groups;wherein data points that are from a more recent seasonal cycle are givena greater weight than data points that are from a less recent seasonalcycle; and determining a temporal weight for each respective pairwiseslope in the set of pairwise slopes based on the respective weightassigned to each respective data point in a data point pair used tocompute the respective pairwise slope.
 19. The one or morenon-transitory computer-readable media of claim 18, wherein therepresentative trend rate is a weighted median that is determined based,at least in part, on the temporal weight for each pairwise slope. 20.The one or more non-transitory computer-readable media of claim 11,wherein the particular seasonal pattern is one of a sparse seasonalhigh, a dense seasonal high, a dense seasonal low, or a sparse seasonallow.